Create the table

CREATE TABLE sales (
    date Date,
    city LowCardinality(String),
    product LowCardinality(String),
    price UInt32
) ENGINE = MergeTree()
ORDER BY date;

Load 10 million rows

INSERT INTO sales
SELECT
    toDate('2020-01-01') + toIntervalDay(rand() % 1826) AS date,
    ['London','Manchester','Birmingham','Leeds','Glasgow'][rand() % 5 + 1] AS city,
    ['Laptop','Phone','Tablet','Monitor','Keyboard'][rand() % 5 + 1] AS product,
    rand() % 1900 + 100 AS price
FROM numbers(10000000);

Run the query

SELECT city, sum(price) AS total, count() AS orders
FROM sales
GROUP BY city
ORDER BY total DESC;